The overall objective of this project is to develop an antagonist for the G-protein-coupled receptor FPRL1 (formyl peptide receptor-like 1) to test the hypothesis that blocking this receptor will prevent accumulation of inflammatory cells into plaques in Alzheimers disease, and thereby prevent neuronal degeneration. FPRL1 receptors have been shown to be expressed on human mononuclear phagocytes which accumulate in plaques and tangles in AD brain. Further, the 42-amino acid form of beta-amyloid has been shown to activate FPRL1 receptors and induce chemotaxis in these phagocytes. Thus, by blocking the FPRL1 receptor we expect to prevent accumulation of these inflammatory cells in AD lesions and consequent neuronal degeneration resulting from inflammatory processes. In this Phase I application, we first propose constructing and validating a cell line that expresses both the FPRL1 receptor and a promiscous G protein that will allow this receptor to couple to the intracellular calcium pathway. This cell line will allow us to rapidly and inexpensively screen a highly diverse library of 14,000 compounds, for antagonist activicty at the FPRL1 receptor. This library includes novel and highly diverse compounds from 50 different structural classes that have rigid scaffold and are amenable to rapid synthetic modification for later lead optimization. Our screening criteria is to find at least one compound that blocks the FPRL1 -mediated increase in intracellular calcium by 50% or more at a concentration of 10 uM. Compounds meeting this criteria will be evaluated further in the following assays: 1) full EC50 curves will be obtained for such compounds in the same intracellular calcium assay; 2) inhibition of peptide W mediated increase in GTP-g-S binding to membranes from cells expressing the FPRL1 receptor; 3) inhibition of radio-iodinated peptide W binding to membranes from cells expressing FPRL1 receptor and 4) inhibition of amyloid beta 42 mediated increase in intracellular calcium in whole cells. Compounds having Ki values of 10 uM or lower in all of these assays (except the peptide W binding assay) will be carried forward to a Phase 2 application in which they will be optimized and rendered potent at the nanomolar level. In Phase II, optimized compounds will be tested in a mouse model of AD for their ability to prevent phagocyte accumulation into brain lesions. Ultimately, the best compound will be licensed to a pharmaceutical company for clinical trials. [unreadable] [unreadable] [unreadable]